Hydrogenated Amorphous Silicon Germanium Alloys Grown by the Hot-Wire Chemical Vapor Deposition Technique

Brent P. Nelson, Yueqin Xu, D. L. Williamson, Bolko Von Roedern, Alice Mason, Stephan Heck, A. H. Mahan, S. E. Schmitt, A. C. Gallagher, John Webb, Robert Reedy

Research output: Contribution to conferencePaperpeer-review

25 Scopus Citations


We successfully grow high-quality hydrogenated amorphous-silicon-germanium alloys (a-SiGe:H) by the hot-wire chemical-vapor deposition (HWCVD) technique using silane and germane gas mixtures. These alloys display electronic properties as good as those grown by the plasma-enhanced chemical-vapor deposition (PECVD) technique, when comparing materials with the same optical bandgaps. However, we grow materials with good electrical properties at high deposition rates - up to 40 angstroms/s, compared to 1-4 angstroms/s for PECVD materials. Our alloys exhibit similar trends with increasing Ge content to alloys grown by PECVD. The defect density, the dark conductivity, and the degree of nanostructural heterogeneity (as measured by small-angle X-ray scattering) all increase with increasing germanium content in the alloy. The nanostructural heterogeneity displays a sharp transition between 9 at.% and 14 at.% germanium. PECVD-grown a-SiGe:H alloys exhibit a similar transition at 20 at.% Ge. The photoconductivity and the ambipolar diffusion length of the alloys decrease with increasing germanium content. For a fixed silane-to-germane gas ratio, all material properties improve substantially when increasing substrate temperature (Tsub) from 220 °C to 375 °C. Increasing Tsub also narrows the optical bandgap and lowers the hydrogen content in the alloys for the same germane-to-silane gas ratio.

Original languageAmerican English
Number of pages6
StatePublished - 1999
EventProceedings of the 1998 MRS Spring Meeting - San Francisco, CA, USA
Duration: 14 Apr 199817 Apr 1998


ConferenceProceedings of the 1998 MRS Spring Meeting
CitySan Francisco, CA, USA

NREL Publication Number

  • NREL/CP-520-24520


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